Comparative Anatomy of Eustachian Tube and Middle Ear Cavity in Animal Models for Otitis Media

Abstract

The comparative anatomy of the normal eustachian tube (ET) and normal middle ear cavity of three animal species (rat, gerbil, and chinchilla) is described relating to the usefulness of these animals as models for otitis media (OM). Routine histological and anatomical techniques and procedures were used. The gerbil and chinchilla, although of different sizes, are quite similar, having hypertrophied middle ear bullae, nearly vertical ET, and similar histology including seromucous glands draining directly into the ET. In contrast, the rat has a small bulla, a nearly horizontal ET, and a large concentration of goblet cells but few mucous glands in the ET. It appears that the chinchilla and the gerbil may serve as alternative models for OM research. Chinchillas and gerbils are relatively free of naturally occurring OM, while the rat has a high incidence of naturally occurring OM.

Morphological Distribution of Middle-Ear Epithelium in the Wistar Rat: A Functional Hypothesis

“…Several observations have shown that the middle-ear mucosa is covered by ciliated epithelium mixed with nonciliated secretory cells, both in man and in animal models [2][3][4][5][6][11][12][13][14][15][16]. Graves and Edwards [17] noted that the lower half of the tube was covered by ciliated cells while the upper part was covered by non-ciliated cells.…”

Mucin gene cDNA sequence characterization in chinchilla middle ear epithelium

“…In addition, the bone at the top of the bulla is very thin, allowing injection of an experimental preparation directly into the middle ear by this route with little trauma to the animal. From a bacteriologic susceptibility standpoint, otitis media is readily induced in the chinchilla after a transbullar bacterial injection of nontypable H. influenzae or S. pneumoniae, but the chinchilla is not naturally susceptible to otitis, unlike other rodent animal models such as the rabbit, guinea pig [17] and the rat [18]. Researchers can thus be reasonably certain that the observed disease is a consequence of experimental manipulation.…”

Technical note for post-auricular route surgery in Mongolian gerbil

“…Indeed, this rodent features an auditory spectrum rather similar to the human's hearing, with good low frequency hearing (Lay, 1972;Müller, 1996;Ryan, 1976;Suberman et al, 2011;Vater and K€ ossl, 2011). In rodents, the middle and inner ears are included in the tympanic bulla (Bulla tympanica, or auditory bulla) that is naturally hypertrophic in gerbils (Bergin et al, 2013;Daniel et al, 1982;Lay, 1972;Mason, 2016). Furthermore, gerbils rarely present with acute otitis media (Bergin et al, 2013;Daniel et al, 1982) which eases the assessment of noninfectious middle ear surgery.…”

“…In rodents, the middle and inner ears are included in the tympanic bulla (Bulla tympanica, or auditory bulla) that is naturally hypertrophic in gerbils (Bergin et al, 2013;Daniel et al, 1982;Lay, 1972;Mason, 2016). Furthermore, gerbils rarely present with acute otitis media (Bergin et al, 2013;Daniel et al, 1982) which eases the assessment of noninfectious middle ear surgery.…”